Clathrina contorta (Bowerbank, 1866) forms an irregular mass of whitish tubes, which are strongly contorted but not as tightly anastomosed as is usual for Clathrina.The surface is finely hispid and the consistency soft. It differs from the very similar Clathrinaclathrus in colour and in the possession of diactines (microscopical examination necessary). It is widespread in the shallow sublittoral along the coasts of Europe, from the Arctic to the Mediterranean.

Taxonomic Description

Colour:Whitish.Shape, size, surface and consistency:Irregular mass of rounded and flattened tubes, which are highly contort, and anastomose here and there. Thickness 5-10 mm, lateral size indefinite. Diameter of the tubes 0.5-1 mm. Surface finely hispid. Oscules at the end of vertically arranged tubes, naked. Consistency soft, fragile.Spicules:(Clathrina contorta spics) Calcareous. Triactines, tetractines and diactines. Triactines regular, rays: 80-90 x 5 µm. Tetractines similar in shape and size, basal triactine system with rays: 80-90 µm, apical ray: 40 x 5 µm. Diactines inequiended, one end thicker, the other with abruptly narrowed sharp point, somewhat sinuously curved: 100-160 x 10 µm.Skeleton: Tetractines and triactines arranged without order in the tube walls with apical rays of the tetractines projecting into the choanocyte chamber. Diactines especially common in the peripheral tubes. Reproduction:August-September. Ecology:Most commonly found on rocks between 10 and 30 m, but occasionally found in the intertidal region under stones.Distribution:From the Arctic to the Mediterranean, including the coasts of the North Sea. Recorded from the southern oceans, but this needs verification.Etymology:contortus (Latin) = twisted or intricate, referring to the shape.Type specimen information:Holotype: BMNH 1950.10.12.6 (dry).

Remarks

This species may be easily confused with the similar Clathrinaclathrus.Microscopic examination is necessary to be certain: C. clathrus has only triactines, lacking tetractines and oxeas; also this is usually coloured brownish yellow; oscules may not normally be seen in C. clathrus.Borojevic and Boury-Esnault, 1987b recorded this species from 350 m off the Bay of Biscaye, but the sizes of the oxeas they quote (500-700 x 44 µm) make it very unlikely that their identification is correct. Source: Burton, 1963.

Burton, M., 1963. A revision of the classification of the calcareous sponges. British Museum (Natural History), London. 693 pp.

Dendy, A. and H. Row, 1913. The classification and phylogeny of the calcareous sponges, with a reference list of all the described species, systematically arranged. Proc. Zool. Soc. London, 53: 704-813.

Gray, J.E., 1867. Notes on the arrangement of sponges, with the description of some new genera. Proc. zool. Soc. London, 1867: 492-558, 2 pls.